1. Technical Field
The present invention relates to an oscillation circuit, an oscillator, an electronic apparatus, and a moving object.
2. Related Art
As a stable frequency-control electronic component in the communication apparatus field, an oscillator has been used that includes, in a package, a vibration piece formed of a piezoelectric body such as quartz and an oscillation circuit that outputs a signal having a predetermined frequency and changes or adjusts an output frequency according to a control voltage input from the outside. In the package of the oscillator, a large number of external connection terminals including a power supply terminal (VCC) that drives the oscillation circuit, a ground terminal (GND), a signal output terminal (RFOUT), and a frequency-control-voltage input terminal (VCONT) are provided. However, when the large number of external connection terminals are provided in the package, it is difficult to reduce the size of the oscillator. Therefore, there has been proposed an oscillator in which a plurality of functions are imparted to one external connection terminal. For example, JP-A-2004-146882 (Patent Literature 1) discloses a digital-control-temperature-compensation reference oscillator including an internal storage device that stores digital temperature compensation data. In the digital-control-temperature-compensation reference oscillator, a power supply terminal also functions as a clock signal input terminal used for writing in the internal storage device. Consequently, the number of external connection terminals provided in a package is reduced to attain a reduction in the size of the oscillator.
With the oscillator disclosed in Patent Literature 1, since the number of external connection terminals can be reduced, it is possible to attain a reduction in the size of the oscillator. However, a clock signal, which is a frequency signal, needs to be superimposed on a direct-current voltage for driving a circuit for oscillation and supplied to the power supply terminal. However, when the clock signal is supplied to the power supply terminal of the circuit for oscillation, since the clock signal is input to the circuit for oscillation as noise, it is likely that frequency accuracy of an oscillation signal output from the oscillator is deteriorated. Therefore, it is difficult to realize an oscillation circuit (an oscillator) that can suppress deterioration in frequency accuracy caused by a reduction in the number of external connection terminals and can be reduced in size.